Nonwoven fabrics and numerous uses thereof are well known to those skilled in the textiles art. Such fabrics can be prepared by forming a web of continuous filament and/or staple fibers and bonding the fibers at points of fiber-to-fiber contact to provide a fabric of requisite strength. The term “bonded nonwoven fabric” is used herein to denote nonwoven fabrics wherein a major portion of the fiber-to-fiber bonding is adhesive bonding accomplished via incorporation of adhesives in the web to “glue” fibers together or autogenous bonding such as obtained by heating the web or by the use of liquid or gaseous bonding agents (usually in conjunction with heating) to render the fibers cohesive.
Spunbonded nonwoven fabrics formed of nylon, polyester, polypropylene, or other polymers are widely used commercially for a number of purposes. Such fabrics exhibit excellent strength and uniformity of properties, and accordingly are desirable for use as coating substrates, construction fabrics, filtration materials, components in automotive fabrics, mattress pads and furniture and bedding backing materials.
The fabrics are produced via the well known spunbonding process in which molten polymer is extruded into filaments, and the filaments are attenuated and drawn pneumatically and deposited onto a collection surface to form a web. The filaments are bonded together to produce a strong, coherent fabric. Filament bonding is typically accomplished either thermally or chemically, i.e., autogenously. Thermal bonding is accomplished by compression of the web of filaments between the nip of a pair of cooperating heating calender rolls thereby setting the thickness.
In autogenous bonding of nylon filaments, the web of filaments is transported to a chemical bonding station or “gas house” which exposes the filaments to an activating agent (i.e., HC1) and water vapor. Water vapor enhances the penetration of the HC1 into the filaments and causes them to become tacky and thus amendable to bonding. Upon leaving the bonding station, the web passes between rolls which compress and bond the web thereby setting the thickness. In autogenous bonding of nylon filaments, the web of filaments is transported to a chemical bonding station or “gas house” which exposes the filaments to an activating agent (i.e., HC1) and water vapor. Water vapor enhances the penetration of the HC1 into the filaments and causes them to become tacky and thus amenable to bonding. Upon leaving the bonding station, the web passes between rolls which compress and bond the web thereby setting the sickness. Adequate bonding is necessary to minimize fabric fuzzing (i.e., the presence of unbonded filaments) and to impart good strength properties to the fabric. Autogenous bonding has been especially used in forming spunbonded nylon industrial fabrics.
Typically, much effort is expended in the production of nonwoven fabrics to maintain and improve the distribution of filaments or uniformity of the fabric. This gives nonwoven fabrics a smooth or “uniform” appearance. In some applications, it is desirable to enhance the properties or change the appearance of the nonwoven fabric. This can be accomplished in carded or needle punched nonwovens through mechanical means or by changing the mixture or recipe of the staple yarn feed stocks. However, it is difficult to accomplish this task on sunpbounded fabrics. A nonwoven fabric with a unique appearance or enhanced properties accomplished by inserting different yarns into the nonwoven fabric would satisfy a need in certain markets.